1. Field of the Invention
The present invention relates to a magnetic disc mounting device and, particularly, to a device for mounting a magnetic disc to a rotary drive shaft of a magnetic recording/reproducing apparatus for use in an electronic still camera and the like.
2. Description of the Prior Art
Recently, there has been developed an attractive electronic still camera system which comprises a combination of an image pickup device such as a charge coupled device (CCD), an image pickup tube or the like with a recording device using as a recording medium an inexpensive magnetic disc having a comparatively larger memory capacity. In this system, a subject is electronically still-photographed and is then recorded into a magnetic disc which is rotating, while a recorded image can be reproduced using separately arranged means such as a television receiver, a printer or the like.
In the above-mentioned camera system, the magnetic disc generally used is in the form of a magnetic disc pack. The magnetic disc pack includes therein a magnetic disc for magnetically recording still image information and the like in such a manner that the magnetic disc can be rotated. Also, the magnetic disc pack is mounted to a magnetic recording device contained within an electronic camera or a reproducing device arranged integrally with or separately from the magnetic recording device, before it is actually used.
In mounting the magnetic disc pack to the magnetic recording device or the reproducing device contained within the electronic camera, it is troublesome and inconvenient to couple a center hole, which is formed in a center core located in the central portion of the magnetic disc in the magnetic disc pack, directly onto a rotary drive shaft disposed on the side of the magnetic recording or reproduction device, and, therefore, there is a possibility that the magnetic disc pack cannot be accurately installed onto the magnetic recording or reproducing device.
In order to avoid the above-mentioned trouble, conventionally, there has been proposed a magnetic disc loading/unloading device. This magnetic disc loading/unloading device is formed of a holder which is supported on a main body of the magnetic recording or reproducing device in such a manner that it is free to open and close. In the loading/unloading device, the magnetic disc pack is inserted into the holder and the holder is then closed, before the magnetic disc of the magnetic disc pack in the holder is loaded onto the rotary drive shaft of the main body of the magnetic recording or reproducing device. In the central portion of the magnetic disc there is provided a center core formed with a central hole. The rotary drive shaft is inserted into the central hole of the center core to rotate the magnetic disc within the magnetic disc pack.
It should be noted here that it is necessary to mount the center core of the magnetic disc to the rotary drive shaft accurately. If the center core is mounted inaccurately or insufficiently, then there is a possibility that a magnetic head may fail to record a signal into the magnetic disc or to reproduce it from the magnetic disc accurately. Also, such insufficient mounting of the center core may have ill effects on the magnetic disc, magnetic head and the like. For this reason, in another conventional magnetic disc pack loading/unloading device, there is proposed a magnetic chuck system in which the rotary drive shaft and the central hole of the center core of the magnetic disc are brought into engagement with each other and a magnet is mounted on the side of the rotary drive shaft to attract the center core toward the rotary drive shaft by means of the magnetic forces of the magnet. However, a sufficient effect cannot be still obtained by this magnetic chuck system.
Also, since there is provided a resilient piece in the center hole of the center core of the magnetic disc of this kind into which the drive shaft is fitted, the center core must be pressed against the drive shaft with a predetermined level of pushing forces so as to be able to mount the center core accurately to the drive shaft against the biasing forces of the resilient piece.
In view of the above-mentioned circumstances, there can be suggested a further system in which a rotary magnetic disc device is composed of a holder and a lid, and there is provided a push pin in the lid, whereby, in loading, the lid is once pushed down slightly toward the drive shaft from its normal position (that is, from the record position to the overstroke position thereof) and the center core is pressed against the drive shaft with the push pin in the lid to thereby mount the center core to the drive shaft. However, in such operation using the overstroke operation to press the center core against the drive shaft, if the lid is overstroke-operated in error during recording, then the push pin may be abutted against the center core so that the center core may be damaged.
Further, according to another magnetic disc mounting device disclosed in Japanese Patent Publication No. 218681 of 1984, there is provided a push pin via a plate spring on the side of a lid and there is provided on the side of the holder a restricting member for restricting the amount of displacement of the push pin, whereby while the lid is being closed the center core is pressed against the drive shaft by means of the push pin and in the closed position of the lid the plate spring is deformed and retreated by the restricting member so as to retreat the push pin to a position in which the push pin cannot come into contact with the center core. However, the disclosed magnetic disc mounting device is found disadvantageous in that the positional relationship between the restricting member and the push pin is complicated. Also, when ejecting, the push pin must by all means push against the center core while the lid is being opened. This center core pushing operation applies loads to the center core and drive shaft, which may deform the center core and drive shaft, resulting in the worsened accuracy of the magnetic disc mounting device.